References

For example, linear hexapeptide 9 was prepared by removing the –Troc protection on 3 to afford 7 and appending the glycine-pyrrole side chain 5 to give 8. After -Fmoc removal, coupling to 4 afforded the desired branched hexapeptide 9, with only the final cyclization and protection group removal remaining. However, compound 9 proved highly unstable and did not succumb to cyclization.